Implementations/suggestions for Multihoming IPv6 for DSL sites

Jeff Wheeler jsw at
Wed Apr 13 19:13:46 UTC 2011

On Tue, Apr 12, 2011 at 4:59 AM, Luigi Iannone
<luigi at> wrote:
> This is not true. There are several works out there showing that the FIB will not grow as you are saying.

Having taken some time to discuss this off-list with Luigi.  I'd
already read the paper he had in mind, which does not address DoS or
prefix growth as the number of multi-homed sites, or single-homed
sites with "PI blocks," increases.

In effect, that paper and other works on this subject fail to consider
what happens when one of LISP's goals actually becomes true: more
wide-spread adoption of its technology to enable branch offices and
other end-users to become multi-homed, or avoid renumbering.

Plain and simple, it does not scale up any better than injecting more
routes into the DFZ, unless you 1) accept macro-flow-based routing; or
2) scale up the size of your FIB along with the much larger number of
prefixes which would be introduced by lowering the barrier-to-entry
for multi-homing and provider-independent addressing.

However, LISP does have non-Internet applications which are
interesting.  You can potentially have multi-homed connectivity
between your own branch offices, using one or more public Internet
connections at each branch, and your own private mapping servers which
know the state of reachability from one branch to the others.  In
effect, it can become "poor man's L3VPN."

Beyond non-Internet applications such as this, I think LISP is useful
largely as a case study for what happens when a bunch of engineers get
together and "solve" some problems they do not understand -- DFZ
size/growth being chief among them.

Like others, I still leave room for the possibility that I am wrong about this.

Jeff S Wheeler <jsw at>
Sr Network Operator  /  Innovative Network Concepts

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